Biodegradation of diethyl phthalate and phthalic acid by a new indigenous Pseudomonas putida

Abstract

Diethyl phthalate (DEP) is one of the extensively used plasticizers which has been considered a priority hazardous pollutant due to its carcinogenic, endocrine disrupter, and multi-toxic effects on humans. The identification of DEP in different parts of the ecosphere has increased the global community's attention to the elimination of this pollutant in a bio-eco-friendly way. In this research, a novel aerobic bacterial strain nominates as ShA (GenBank accession number: MN298858) capable of consuming DEP as carbon and energy sources, was isolated from the upper phase (0-10 cm) of Anzali international wetland sediments by enrichment culture method. Morphological characteristics and 16S rRNA gene sequence analysis demonstrated that strain ShA belonged to Pseudomonas putida. The substrate utilization test demonstrated that strain ShA was able to grow in mineral salt medium containing dimethyl phthalate (DMP) and phthalic acid (PA) isomers including terephthalic and isophthalic acid. Degradation assay showed strain ShA completely degraded 200 mg/L DEP within 22 h (pH 7.0, 30 °C). Surprisingly, PA as the main intermediate of DEP biodegradation was identified by GC-FID. Moreover, the rapid degradation of 2000 mg/L PA to CO₂ and H₂O was viewed in 22 h by strain ShA. The possible route of DEP degradation was DEP directly to PA and then PA consumption for growth. This study obtained results that provide a great contribution to applying strain ShA in the biodegradation of low molecular weight of PAEs and PA isomers in natural ecosystems. This is the first report of a P. putida strain able to degrade DEP and PA.

Keywords: DEP; Phthalic acid; Pseudomonas putida; Sediments.